1. Field of the Invention
The present invention relates to an electronic musical instrument and, more particularly, to a musical tone control mechanism for controlling a volume level and the like during a performance.
2. Description of the Prior Art
Various types of electronic musical instruments have been developed, and such an electronic musical instrument generally comprises a sound source oscillator, an acoustic waveform shaper, an amplifier, a speaker, and various electronic control circuits and generates musical tones upon operations of various buttons arranged on a keyboard and an operation board. In such an electronic musical instrument, musical tone adjustment operations such as operations for adjusting tone colors, pitches and volume levels of electronic musical tones generated by the instrument are required. These musical tone adjustment operations are preferably performed in correspondence with keyboard areas of melody and musical accompaniment parts.
As a conventional musical tone control mechanism for an electronic musical instrument, an electronic musical instrument having a rotary volume control unit along a keyboard is disclosed in Japanese Utility Model Publication No. Sho 59-1270. In this conventional electronic musical instrument, a columnar volume control member longer than the keyboard is arranged along the keyboard, and the volume control member is rotated by a hand, which also operates the keyboard at the same time, to manually adjust the volume level.
In the conventional electronic musical instrument, since one columnar volume control member is arranged along the keyboard, it is impossible to adjust musical tones in correspondence with performance parts such as melody and musical accompaniment parts corresponding to the keyboard areas. In addition, the performer may erroneously operate the rotary body during a performance of a keyboard part which does not require musical tone adjustment, such as a keyboard solo part.
This rotary body can only control the volume level, but cannot adjust tone colors, pitches, and other musical tone functions. In order to adjust these additional musical tone functions, other control mechanisms must be arranged, thus complicating the arrangement of the electronic musical instrument.
Furthermore, it is difficult to operate the rotary body by a palm of a hand with an appropriate force, and a rotating shaft of a volume control connected to the rotary body is overloaded to deform the rotating shaft or result in failure in the volume control.